Marshfield double murder suspect under investigation in Florida aggravated battery case

A booking photo of Christopher M. Keeley, 27, was arrested Friday night by Miami Beach police on charges he murdered a Marshfield couple in their home. He also faces an investigation by Miami Beach police for his involvement in an aggravated battery case.Miami-Dade County

The suspect accused of brutally murdering a Marshfield couple is also believed to have been involved in a Florida assault Friday that left a man hospitalized and in critical condition, according to Miami Beach police.

Christopher M. Keeley, 27, was arrested by police in Miami Beach, Friday night after Massachusetts law enforcement officials charged him with the murders of Carl “Buddy” Mattson and Vicki L. Mattson.

Police in Miami Beach located Keeley while they were responding to a report of aggravated battery at 7:25 p.m. Friday near the intersection of 41st Street and North Meridian Avenue, according to Miami Beach Police Officer Ernesto Rodriguez, a department spokesperson.

At the scene, police found a man suffering from a head injury and he was transported to Jackson Memorial Hospital’s Ryder Trauma Unit, where he was in critical condition Sunday, Rodriguez said in an e-mail to the Globe.

Keeley was found nearby and arrested on the warrant issued in the Marshfield murder case, according to Rodriguez.

Miami Beach police are also looking into Keeley’s role in the battery case.

“It is believed Keeley is also involved in the Miami Beach incident. However, charges are pending the forensic analysis of the evidence located,” Rodriguez said in an e-mail to the Globe.

Keeley suffered a laceration to the upper left part of his face, had scrapes on his back, and pain in his left shoulder, according to a Miami Beach police report. He refused treatment at the scene.

He is being held at Miami-Dade county’s Turner Guilford Knight Correctional Facility, Rodriguez said.

Christopher M. Keeley, 27, was arrested by police in Miami Beach, Friday night after Massachusetts law enforcement officials charged him with the murders of Carl “Buddy” Mattson and Vicki L. Mattson.

It was not clear what would happen to the Massachusetts case if Keeley were to be charged with a crime in Florida.

Beth Stone, a spokesperson for the Plymouth district attorney’s office, declined to comment on the Miami Beach case Sunday.

Attorney Kathleen Fay, who is representing the Keeley family, said in a text message Sunday afternoon that they were not aware of the Miami Beach aggravated battery case. She declined further comment.

Keeley, who is from Weymouth, had been the subject of a manhunt after Marshfield police found the Mattsons’ bodies inside their home Tuesday. They had been bludgeoned and stabbed to death. The couple’s dog was also found dead and is part of the investigation.

He had been staying with the couple in their Gotham Hill Drive home, and he told a friend the night of Nov. 25 that he had attacked them, according to court papers.

Carl Mattson and Keeley got into an altercation over the dog, which had been barking, Keeley told his friend. The conflict led to the killings, according to court papers.

“Keeley did not describe how he killed them, but stated that there is a 1 percent chance they are alive,” investigators reported.

The Mattsons were last seen alive on Thanksgiving Day, when they celebrated the holiday with relatives. Carl Mattson, 72, and Vicki Mattson, who would have turned 71 Wednesday, met as teenagers while growing up in Weymouth.

They would have celebrated their 50th wedding anniversary next year, according to their family.

Visitation hours will be held Wednesday from 4 to 8 p.m. at the C.C. Shepherd Funeral Home in South Weymouth and funeral Mass will be said at 10 a.m. Thursday at Old South Union Church, also in South Weymouth, according to their death notice. The couple will be buried together.