LITTLETON, Colo. (AP) _ Three young men dressed in black trench coats opened fire in a suburban high school today, scattering students as gunshots ricocheted off lockers in what police called a suicide mission. Twenty-five people may have been killed, including two gunmen, the sheriff said.

The suspects' bodies were found inside the library at Columbine High School hours later, said the Jefferson County sheriff, John Stone. He said the dead gunmen were students. Their bodies had devices that may have been bombs, authorities said.

``It appears to be a suicide mission,'' Stone said.

Some 4 1/2-hours after the shootings, police led away a student from the school in handcuffs.

``He's one of the ones who shot at us,'' said Chris Wisher, another student.

It was not immediately know if the others killed were students or teachers, police said. Explosions also were heard in the school, and police said they had to search for bombs, slowing them down as they looked for victims.

Nearly two hours after the 11:30 a.m. shooting, SWAT team members entered the building and 15 to 20 students fled. The frightened students ran out with their hands in the air and were later frisked by police. Several other groups of youths ran from the school in the following hours after an armored car was brought to an entrance for cover.

SWAT team members searching the building were able to see some wounded students but couldn't reach them because the area wasn't secure, said Steve Davis, sheriff department spokesman.

Television images, broadcast nationwide, showed police cars and ambulances at a staging area near the school, and helmeted officers in camouflage gear. At one point, a bloodied young man dangled from a second-floor window, his right arm limp, and was helped down by two SWAT team members. His condition was not immediately known.

``We believe there are a few more victims,'' Davis said earlier. ``We're hearing from deputies who can see from their vantage points more victims.''

One student, Kami Vest, called her father as she hid in the school with 30 other students. ``They have been able to call out on a cell phone and tell us they are OK,'' Dale Vest said. He said at midafternoon that she remained in hiding.

President Clinton asked Americans to pray for the students, parents and teachers.

Shortly after the school was stormed, three youths wearing black were stopped by police in a field near the school. The Colorado Bureau of Investigation told KUSA-TV the three were friends of the gunmen and were taken in for questioning.

Some witnesses said there were two gunmen and the shootings took place around the school, including the cafeteria and library.

``At first we just though they were firecrackers until we saw the guns come out of the trench coats,'' said student Justin Woods.

``They walked down the stairs and they started shooting people,'' said another student, who gave her name as Janine. ``We didn't think it was real and then we saw blood.'' Her voice broke with anguish as she spoke.

She said it was two young men, wearing black trench coats. The sheriff said the three gunmen were wearing military fatigues.

``They were shooting people and throwing grenades and stuff. ... Me and my friends got to my car and drove off,'' Janine said.

Bob Sapin, another student, also said the gunmen were all in black, in trench coats and masks.

``When they started walking down the hallway, I ran and I ran and I hid in the bushes,'' he said.

Eight to 10 students in the school wear black trench coats every day, students said. Josh Nielsen said they are known as the ``Trench Coat Mafia.'' Another student, Jason Greer, called them ``jerks.'' ``They are really strange, but I've never seen them do anything violent,'' he said.

Sean Kelly, a 16-year-old junior, said members of the group kept to themselves and were ``kind of gothic. They are wearing dusters. They wear them every day, all black clothing.''

``They're into guns and stuff like that,'' he added.

At the adjacent Clement Park, students were shaking and crying as parents wandered about, looking for their children. Police helicopters whirled overhead and hundreds of police officers patrolled the area and a nearby park.

At least 19 people were taken to hospitals, including a girl who suffered nine gunshot wounds to the chest. Kari Mackecher, spokesman for HealthOne, which runs Swedish Hospital, said four students were taken there, all in serious condition but conscious, and a fifth was en route.

Five other hospitals reported getting 14 people, at least one of them in critical condition. The 20th injured person was the young man taken out of the school window at midafternoon.

Denver and Littleton police, and Jefferson County and Arapahoe sheriff's deputies were helping on the scene.

Columbine High is in the middle-class suburb of Littleton, population 35,000, southwest of Denver. Single-family homes line winding roads through the neighborhood.

The school opened in 1973 and has an enrollment of about 1,800. Nearby schools were put on a lockdown status, with students prohibited from entering or leaving.

A series of school shootings since 1997 shocked the nation and led to calls for tighter security and closer monitoring of troubled students. Two were killed at a school in Pearl, Miss., three at West Paducah, Ky., five at Jonesboro, Ark., and two at a school in Springfield, Ore.