Sheriff's officials said a 26-year-old man and an accomplice were behind bars Friday on suspicion of killing his 73-year-old grandmother in her mobile home in Alpine during a robbery.

Brandon Allen Hayes and Jeffrey Carl Reed were arrested at the San Ysidro Port of Entry at separate times Thursday night as each re-entered the country from Mexico, according to San Diego County sheriff's homicide Lt. Dennis Brugos.

Reed allegedly helped Hayes kill his grandmother, Eunice Cothron, last weekend.

"At this time, it is believed that the motive for this crime, at least in part, was robbery," according to Brugos.

Cothron's body was discovered in her home at the Alpine Mobile Home Estates in the 2400 block of Alpine Boulevard around 9 p.m. Saturday, Brugos said.

The cause of death has yet to be released.

Neighbors told News 8 that Cothron had taken out a restraining order against Hayes, who they said sold her car to drug dealers.

"She's a nice gal," a man told the television station. "I can't understand why someone would do that to her."