HARRISBURG, Pa. (AP) — At least three men recently paroled from Pennsylvania prisons have been arrested in unrelated homicides over the past two months, leading to calls from prosecutors and corrections officers for a review of the state's parole practices.

The men were arrested within a couple days of one another this month, all in cases with connections to domestic violence.

One is a convicted murderer who got out of prison in March and is now charged with killing an 8-year-old boy two weeks ago in the western Pennsylvania city of New Castle.

Two other parolees released from prison in the past two years are facing charges in the beating death of a 2-year-old Baltimore boy and the strangulation of a 49-year-old Hershey woman.

"I think the nature of the cases and the cluster is certainly what is alarming," Jennifer Storm, the state's victim advocate, said Monday. "When you're talking about domestic violence and children, these are especially horrific and heinous crimes."

The arrests come as the state has worked to lower the state's prison population, in part by limiting the length of a prison stay for parole violators and providing parolees with more services in the community, such as skills training, mental health counseling and substance abuse treatment.

In recent years, the ranks of state parolees grew by about a fourth, to 31,000, as parole violators spent less time in prison and more on the streets.

The Pennsylvania District Attorneys Association said it was troubled by the cases, and it urged a review.

"We should all expect that there will be an exhaustive review — by an outside entity if necessary — of each case in order to determine what, if anything, went wrong and what reforms can be implemented going forward to help prevent additional tragedies," Lindsay Vaughan, the organization's executive director, said in a statement.

Meanwhile Monday, police charged another parolee in last week's fatal shooting of an off-duty Pittsburgh police officer.

The Pennsylvania State Corrections Officers Association cited the case of Keith Burley in calling for a review of parole practices.

Burley, 43, who pleaded guilty to third-degree murder in a 1999 shooting, is accused of stabbing his girlfriend's 8-year-old son to death during a domestic dispute July 8.

The corrections officers association said state officials must be sure that violent offenders aren't being released, review its policies and be transparent on how many parolees have committed crimes.

Burley had not committed any behavioral infractions for about five years, but stabbed a fellow inmate in the neck with a pencil and committed more than 27 instances of misconduct during his prison time, the organization's president, Larry Blackwell, said in a statement.

"Despite this, he was released when he reached the minimum of his 20- to 40-year sentence," Blackwell said.

Burley's lawyer did not return a telephone call Monday.

The Department of Corrections said the men had complied with the terms of their parole up to the time of the alleged homicides. It released a general statement, called a "green sheet," explaining in general terms why each man won parole, but it declined to release a more detailed document, a 12-page "parole decisional instrument" produced by the Board of Probation and Parole.

Also facing charges are David Haas, 34, and Calvin Purdie, 33.

Haas was arrested in the June 29 beating death of his girlfriend's 2-year-old son in Baltimore. Purdie was charged in the May 23 strangling of the 49-year-old mother of his girlfriend in her Hershey home before he allegedly set fire to the house to cover up the crime.

Haas' criminal record involved drugs and theft. Purdie pleaded guilty to aggravated assault in 2014 and, after he got out on parole, he served another six months in prison last year for a parole violation after he pleaded guilty to simple assault and drug and motor vehicle violations, according to state court records.

The Baltimore County public defender's office did not return a telephone call about Haas. The Dauphin County public defender's office said Purdie had not yet been assigned a lawyer Monday.