Harvard Police on Wednesday arrested a man who allegedly was threatening to stab his girlfriend in front of Children's Hospital at the Harvard Medical School, police officials said yesterday.

Officers Leon Bathwaite and Elizabeth McClure were on routine patrol at 6:30 p.m., when they spotted Pedro Greene "holding a silver knife in a threatening manner," police reports indicated.

When Greene saw the officers, he attempted to hide the knife. The weapon was discovered after the officers conducted a body search of the suspect.

The incident, which took place outside 300 Longwood Ave., happened after the suspect and his girlfriend had a heated argument.

Greene was arrested and turned over to Boston police.

In an unrelated incident, Harvard police arrested a man on Western Ave. in Brighton for threatening a Boston resident with a gun on Tuesday afternoon.

The alleged victim, Michael Jones, told Officer Robert Cooper that the suspect had broken into his brother's car.

According to police, the suspect told Jones, "Get the fuck away or I'll kill you." The man then pulled a gun on Jones.

Cooper chased the suspect on foot and by car before finally stopping him, police reports indicate. "It was a good chase," officials said.

Police did not find a gun on the suspect, but they did discover a Buck knife after conducting a body search.

The suspect was charged with breaking and entering a motor vehicle and assault with a dangerous weapon. He was arraigned on Wednesday in Boston 14th District Court.