In the immediate aftermath of a birthday bash shooting in Baker this spring, emotions of shocked and grief-stricken party attendees flowed online to social media websites. Rumor was rampant.

But at least one post by a girl on Instagram led detectives to a key witness. She told police she could identify the shooter charged with gunning down three teens on a dance floor in late March.

Not long after speaking with the eyewitness, a detective scoured her Instagram profile, according to a search warrant recently filed in court, looking for information that might show whether she recently changed her password. The warrant also sought financial data associated with the account, photos or other uploaded materials that might have been deleted and other user registration information in an effort to sniff out any potentially useful leads.

The case highlights an investigative tool wielded now more than ever by law enforcement amid the explosive growth of digital communication: social media.

Seeking to harness a torrent of data gushing from smartphones and computers, authorities are increasingly surfing Facebook, Twitter and Youtube, among other popular sites, for investigative leads and evidence they use to solve crimes. As if patrolling a neighborhood, police monitor social media websites to contact witnesses, identify suspects and look for chatter that might signal potential violence.

“People will go on social media and brag about acts that they’ve committed,” said Capt. Doug Cain, a State Police spokesman. “Certainly, if we have access to it and find it, we’re going to make that part of a case.”

In many cases, investigators are diving below the public surface of social media, obtaining warrants to search private Facebook messages and collect network histories they hope will guide them to fugitives.

In late April, investigators with the Louisiana Department of Justice’s Fugitive Apprehension Unit obtained geolocation information and private messages connected to the Facebook profile of a New Orleans woman accused of filing a fraudulent tax return in the name of a professional athlete. Within a week, she was arrested.

Early last year, deputies with the East Baton Rouge Parish Sheriff’s Office noticed chatter on social media that included threats of violence in and around the Mall of Louisiana. Equipped with that information, investigators increased their patrols for the night. Although they spent hours breaking up disturbances among hundreds of minors, no one was injured, said Casey Rayborn Hicks, a Sheriff’s Office’s spokeswoman.

Social media can be helpful in other situations, too, she said.

“People have admitted to crimes on Facebook,” Hicks said. “That information can then be used to find out if it’s a valid post.”

Police in New Orleans recently have spent time researching Facebook profiles of gang members for evidence of drug dealing and gun slinging, court documents show, even gaining access to accounts of slain gang members.

“The technology that has become available to law enforcement is unbelievable, and if you’re not on the cutting edge when it comes to social media investigations, you’re going to miss out on some valuable information,” Covington Police Chief Tim Lentz said. “People are not the brightest when it comes to what they post, and absolutely cases have been made by their Facebook posts and their Twitter pages.”

A widely distributed survey by the International Association of Chiefs of Police last year found that 86 percent of law enforcement agencies are using social media in criminal investigations, up from 62 percent in 2010. All together, 96 percent of agencies surveyed in late 2013 reported using social media in some capacity. More than half are even using Facebook to create fake profiles for undercover investigations, which actually is a violation of the website’s terms of use.

“Social media has really become an integral part of what law enforcement does, both from an investigative standpoint and for community outreach and engagement,” said Nancy Kolb, a senior program manager at the International Association of Chiefs of Police.

Trooper First Class Jared Sandifer said he used Facebook on a regular basis when he worked as a computer-based investigator at State Police. In at least one case, social media helped authorities nab a fugitive. “He actually posted online where he worked,” Sandifer said. “And we went and found him at his job. ... That’s happened several times.”

John Selleck, a FBI agent in New Orleans, said authorities encountered a situation not long ago in which a man holding hostages accessed the Internet through social media.

“Had we not been monitoring that,” Selleck said, “we would have missed out on this insight into this deranged individual’s mindset with regard to hostages. So it’s not only the protracted, long-term investigation, but it’s also in critical incidents where we’re looking at this.”

Social media also has enabled law enforcement to engage in a two-way conversation with the public. Cain, the State Police spokesmen, said his agency, which has more than 75,000 “likes” on its Facebook page, receives tips from the public on Facebook that have resulted in arrests.

Until recently, many investigators had been self-taught in their use of social media. But more agencies are now receiving formal instruction about navigating the digital world, said Lauri Stevens, founder of LAwS Communications, a Massachusetts organization that hosts conferences dedicated the use of social media by law enforcement. Nearly all large police departments have some sort of system in place for watching social media, she said, and some employ “very high-end tools.”

“The investigators I work with tell me there isn’t a case they work any more that doesn’t have at least some kind of connection with social media,” Stevens said. “It just doesn’t happen any more because social media is just too prevalent.”

In New Orleans, court documents show a police detective recently used a Facebook profile photograph to identify a suspect in an aggravated burglary in which a saw-wielding man barged into a home and attacked a resident.

A similar tactic recently was employed by federal authorities who recognized an unmistakable Facebook profile photo of a fugitive they were seeking to identify. The suspect, Kory D. Kreider, allegedly tried to run over federal agents in a Burger King parking lot in Metairie after accepting a shipment of Xanax at a nearby mailing center.

“It’s fair to say the vast majority of the investigations we do have some kind of connection to social media, whether it’s Facebook accounts, video messaging, Snapchat or Kik,” said Bryan Cox, a spokesman for the U.S. Immigration and Customs Enforcement, referring to the agency’s role in child pornography and human trafficking investigations. “Next year, it will be ones we’re not even talking about yet.”

Follow Ben Wallace on Twitter, @_BenWallace. Follow Jim Mustian on Twitter, @JimMustian.