New Orleans police on Wednesday arrested a man suspected of killing a 15-year-old boy and wounding seven other people at a graduation party Friday night in Gentilly.

Zachary Gibson, 19, was booked with second-degree murder. His bail was set at $750,000, according to Orleans Parish Prison records.

Gibson allegedly opened fire at a crowded party in the 6200 block of Eads Street about 11:20 p.m. Friday, mortally wounding Tremaine Robertson and wounding four females and three males.

Robertson, who was in town from his home in Spring, Texas, died a short time later at Interim LSU Hospital from a gunshot wound to the head.

The other victims’ injuries were not serious, police said.

Police have said an argument among partygoers led to the gunfire. They have not said what the argument was about.

Eyewitnesses described a chaotic scene, with hundreds of people fleeing the residence as between 15 and 20 gunshots were fired.

The party was being held in honor of JeShan Vail, a 17-year-old who lived at the house and was finishing his senior year at George Washington Carver High School.

Vail said Robertson was his half-brother and came to town for the graduation party from his home near Houston. He described Robertson as having passions for basketball and fashion.

According to Vail, there were about 250 people at the party. He said he and his friends charged $5 per person to recoup expenses associated with the event.

When the shooting happened, he said, he was standing right next to Robertson.

“All I saw was blood on his face and head,” he told a reporter a day after the shooting.

He said Robertson was an innocent bystander and not involved in the conflict that precipitated the shooting.

Vail also said he didn’t know the shooter or shooters.

“We never saw them,” he said.

Authorities arrested Gibson about 7:30 a.m. Wednesday at his home in the 2400 block of Sixth Street.

Gibson did not give a statement to police.

Detective Barret Morton is leading the investigation.

Follow Danny Monteverde on Twitter, @DCMonteverde.