A 20-year-old Rockville man was rescued by Montgomery County police and firefighters last night after he had climbed nearly 300 feet to the top of a radio tower in Kensington and, according to some witnesses, threatened to jump down.

Police said Joaquin Betancourt of 13211 Twinbrook Pkwy. was escorted safely down from the tower at University Boulevard and Veirs Mill Road around 10 p.m. while as many as 300 people watched from the ground.

Betancourt, who suffered cuts on his arms in the incident, was taken to Montgomery General Hospital for a mental evaluation, police said.

A county fire official said Betancourt was spotted climbing the the tower -- used by radio station WMOD -- shortly after 8 p.m. When rescue personnel arrived, Betancourt was about halfway to the top and still climbing, said Assistant Fire Chief Jim Stanton.

Eddie Schoemaker, an attendant at a nearby gas station, said he saw Betancourt reach the top of the tower, walk around a platform there and shout, "Get those police out of here!" and "I'm going to jump."

Police negotiator Joseph Hock and firefighter Norman C. Haugen climbed the tower ladder after Betancourt and were able to attach a leather belt and a rope around his waist, Stanton said. The firefighter helped Betancourt descend the ladder while the police officer remained at the top holding the rope, he said.

Stanton said Betancourt apparently gained access to the tower after climbing an eight-foot-high security fence topped with barbed wire.

"Nobody saw him come in," said the tower's owner, Judy Carver, who was called to the scene. "We haven't figured it out."