A five-hour standoff between Prince George's County police and a Greenbelt man who had fatally shot his girlfriend ended yesterday when authorities sent a robot into the couple's apartment to help subdue the suspect, police said.

Craig Allen Smith, 22, was charged with first-degree murder in the shooting of his live-in girlfriend, Cynthia Marie Wilkinson, 24, police said.

Smith shot Wilkinson yesterday morning with a shotgun after an argument in their apartment in the 8500 block of Greenbelt Road, police said.

A friend of Wilkinson's who was visiting the apartment when the shooting occurred escaped by jumping out a window of the second-story apartment, police said. She ran to a neighbor's home to call police, but police said that when they arrived, Smith was armed with a shotgun and refused to come out.

Police negotiators communicating with Smith by telephone were unable to persuade him to surrender, said Sgt. Alan Day, a police spokesman. About 2:30 p.m., police decided to use a three-foot tall, 480-pound remote-controlled robot to enter the apartment, Day said.

The robot, which often is used by the Prince George's Fire Department to disarm explosive devices, found Smith hiding in a bedroom closet underneath a pile of clothes. The robot, transmitting the scene to police by a television camera, opened the closet door and removed the clothes that buried Smith, Day said.

Smith grabbed the clothes from the robot and began to cover himself with them once again, Day said.

Acting on the remote-control directions of a technician, the robot then used a high-pressure water gun to knock the shotgun out of Smith's hands and disorient him, enabling the county police department's version of a SWAT team to arrest Smith, said Cpl. Keith Evans, a department spokesman.

Wilkinson apparently had told Smith on Wednesday night that she wanted to end their relationship, causing an argument between the two. The dispute resumed yesterday morning, and Smith shot Wilkinson while they argued, Evans said.

Wilkinson's friend, who police declined to identify because she is a potential witness, told police that Smith sexually assaulted her yesterday, although it was unclear whether the attack occurred before or after the shooting, Evans said. Sexual assault charges were also filed against Smith.