When Alvin Richardson was arrested and accused of shooting and killing his friend Barry Blackwell in the cab of a pickup truck and then tossing him onto the South Broad Street overpass, the commander of the New Orleans Police Department’s Homicide Division said he could not offer a rationale for the killing.

“Attempting to assign a logical explanation to his irrational actions is something we haven’t been able to do,” Sgt. Nicholas Gernon said Feb. 28, the day after the killing.

The shooting occurred about 2:30 p.m. near Tulane Avenue and South Broad Street, a stone’s throw from New Orleans police headquarters and the Criminal District Courthouse. One of the bullets also hit a courthouse employee, who was treated for injuries that were not life-threatening.

Gernon alluded at the time to Richardson’s history of mental illness, and a 1991 psychiatric examination shows that Richardson was diagnosed with schizophrenia and “mild mental retardation.” Psychological testing indicated that his IQ was in the mid-60s, far below average.

He was in jail at the time of the exam in connection with another violent incident, in which he shot a New Orleans police officer.

In that case, Richardson initially was considered “incompetent to proceed to trial” and was sent to the Feliciana Forensic Facility. He was confined there for nine months in 1991 before eventually being found fit to face trial on charges of attempted first-degree murder and being a felon in possession of a firearm. He pleaded guilty to those charges and served five years in prison, according to the state Department of Corrections.

The charges stemmed from a 1989 incident in which Richardson pointed a gun at a pedestrian in Bywater and then led police on a wild chase. While fleeing in a stolen car, Richardson shot a rookie New Orleans police officer in the chest, according to a Times-Picayune report from the time.

Richardson was found after police were called about a wounded man in the 1900 block of France Road. He was booked on two counts of attempted first-degree murder and one count of being a felon in possession of a firearm. But he was then judged to be “presently ‘insane’ ” and was committed to the Feliciana facility on March 12, 1991, according to court records.

Richardson’s six-month status report found that his mental state improved while he was confined. At first, he was withdrawn and refused to take part in group therapy sessions, according to the report.

However, “the patient’s participation has slowly improved from often complaining of hearing voices saying ‘kill someone’ to seldom hearing the voices,” wrote Dahn Savell, a mental health clinical social worker at the time.

In November 1991, a panel appointed to assess Richardson’s mental state found that he was competent and the trial could proceed.

Almost 25 years later, Richardson is being held in Jefferson Parish on gun charges after he was arrested in Gretna the day after the Broad Street shooting.

He reportedly called Gretna police from a payphone to complain that someone was following him. Richardson claimed, “Some people (are) outside my hotel room, and they said they were coming in to get me,” said Capt. Russell Lloyd, of the Gretna Police Department.

During the conversation, he also said he had been on the overpass when Blackwell was shot the day before, leading Gretna police to discover he was wanted in New Orleans.

Gernon, of the NOPD, said the Toyota Titan that Richardson was driving contained “several spent shell casings on the floorboard, as well as a large amount of blood on the front passenger seat.”

It’s unclear when Richardson will return to New Orleans to face murder and attempted murder charges.

Spokesmen for the Orleans Parish and Jefferson Parish district attorneys’ offices did not respond to calls Monday.