A man who was in custody in a Delaware jail in April was being described by his probation officer as the prime suspect in the Philadelphia shooting death of his mother. But he wasn’t charged in her killing, and was released later that month.

In the weeks following, Keith Gibson allegedly went on a crime spree that left three people dead.

Gibson, 39, was arrested in Wilmington on Tuesday on robbery charges, and authorities say additional charges are pending. Police in Philadelphia and Delaware have linked him with at least a half-dozen killings this year.

A review of what happened inside the Delaware courtroom, however, raises questions about the decision to release Gibson — who is to be charged in Saturday’s murder of a Dunkin’ Donuts manager in Fairhill.

Probation officials first filed a violation against Gibson in February after his mother was found dead. They alleged he was in Philadelphia, which violated the terms of his release on a 2010 manslaughter conviction.

In an April court hearing, probation officers described Gibson as having a “very extensive history of violence” and recommended that Superior Court Judge Vivian L. Medinilla sentence him to 6½ years in prison.

Two weeks later, on April 27, Gibson’s public defender told the judge he had community support and job prospects if he were to be released immediately, according to Jason Miller, a spokesperson for the Delaware Department of Corrections, which oversees the state’s probation and parole office.

He said probation officers didn’t object. The judge sentenced Gibson to 30 days and granted him time served, meaning he was released that day on probation.

Linda M. Carmichael, chief staff attorney at the Delaware Superior Court, said Medinilla would not comment on a pending matter.

Less than three weeks after Gibson was released, Leslie Lizet Basilio, a 28-year-old employee at a MetroPCS store in Elsmere, Del., was fatally shot during a robbery. Investigators there believe Gibson may be the perpetrator, Philadelphia Police Chief Inspector Frank Vanore said.

Then, last Saturday, Christine Lugo, the 41-year-old manager of the Dunkin’ Donuts at 532 W. Lehigh Ave., was shot dead in the course of a robbery. An arrest warrant has been approved to charge Gibson with murder in the killing, and additional charges are likely, said Jane Roh, a spokesperson for the Philadelphia District Attorney’s Office.

Detectives also believe Gibson is linked to the fatal shooting of a man during a robbery in Delaware early Sunday, as well as two more robberies in Delaware this week, Vanore said.

Gibson was arrested Tuesday in Wilmington about a block away from where he allegedly robbed a Rite-Aid. When he was arrested, he had been wearing a bulletproof vest. He was charged with robbery and related offenses and is being held in Delaware. It was unclear Friday when he’d be extradited to Philadelphia, and Wilmington police didn’t respond to messages.

Gibson’s Delaware probation officer wrote in papers submitted to Medinilla that Gibson has “documented anger issues” and a lengthy criminal history that includes nine felony convictions and more than a dozen probation violations. The most serious of those was a manslaughter conviction following the 2008 robbery and fatal shooting of a man in Wilmington. Gibson was imprisoned for more than a decade for that crime and paroled in June 2020.

Gibson was released last summer to a community corrections facility, Miller said. While he was there, a judge found him in violation of his probation for fighting, and he was sentenced to another six months in prison and a year-and-a-half of probation.

He was released in December, Miller said, and told officials he was homeless and requested a transfer to Philadelphia. At the time, he was prohibited from leaving Delaware and from carrying a firearm. The transfer was later approved.

On Feb. 8, Gibson’s mother, Christine, a 54-year-old mental-health counselor, was found shot to death at her place of work in Philadelphia.

The next day, Gibson’s probation officer got a call from the Philadelphia Police homicide unit identifying Gibson as a suspect in the death of his mother, the probation officer wrote in court records. The Department of Corrections filed a probation violation against Gibson for being out of state. He was arrested in Philadelphia and returned to Delaware in late March.

The probation officer initially recommended that Medinilla sentence Gibson to 6½ years in prison, writing that while the investigation was ongoing, “early reports suggest Mr. Gibson’s mother informed numerous friends and family that if something were to happen to her, her son would be the one responsible.”

Medinilla found Gibson in violation on April 13 and deferred his sentencing, Carmichael said. She said Gibson returned for sentencing on April 27, when he was released.

His transfer to Pennsylvania was approved on May 10, and he checked in with state parole officers in Philadelphia on May 12, a Pennsylvania Department of Corrections spokesperson said.

Three days after that check-in, Basilio was killed at the Metro PCS store in Elsmere.

In addition to the alleged killing of Gibson’s mother and the three robbery-related homicides in May and June, authorities say Gibson is a suspect in a double homicide in January in which two men were found dead in the back of the Al-Madinah Traders store in North Philadelphia.