A standoff Wednesday morning between police and a Randolph man in a house 100 yards from Teresa C. Hamlin School ended with no injuries, police said. The man threatened to use a shotgun if Kennebec County sheriff deputies entered, after telling his wife he wanted to commit suicide, said Ryan Reardon, chief deputy for the Kennebec County Sheriff’s Office. Classes at Hamlin school were canceled for the day when the standoff was first reported. The sheriff’s office got a call from the man’s wife at around 7:15 a.m., saying that the man had a knife up to his throat and was threatening to kill himself, Reardon said.