1.   Officer Del Debbio suspected that the man might be the one who dropped the shotgun.

2.   One teen-ager ran toward a waiting subway train and dropped a shotgun near the open doors where Del Debbio was standing.

3.   The incident that linked the two men began when a youth dropped a shotgun on an F train that had stopped in the station, and it went off.

4.   The remaining shot, they said, occurred when a suspect dropped his shotgun and it went off.

5.   While trying to escape, one youth dropped a shotgun inside the last car of a stopped Queens-bound F train, and the weapon discharged.