A 36-year-old man was arrested this morning after he allegedly armed himself with a shotgun, threatened several family members and barricaded himself inside his San Francisco home, police said.The incident began early this morning in the unit block of Montcalm Street when Eric Daniel Johns got into a fight with two of his brothers. Police Capt. Paul Chignell, who responded to the dispute and eventually detained the suspect, said it was Johns’ mother who initially notified police.Johns’ 92-year-old grandmother and 12-year-old son were also at the home at the time of the fight, Chignell said. Officers from the Police Department’s Ingleside District arrived at the home at about 4:15 a.m. and contacted Johns’ mother, who said her son had threatened to kill everyone inside the home, Chignell said. Officers also learned Johns had access to a shotgun.While officers were investigating the incident, Johns allegedly yelled at the officers from the top floor of the home and told them to get out of the house.”He yelled at the officers in an obscenity-laden tirade,” Chignell said. Officers managed to escort the 12-year-old son and Johns’ mother outside of the house, but Johns remained in the home with his grandmother.The suspect’s brothers had left the home prior to police arrival.Responding officers set up a perimeter around the home and waited for additional units to arrive.Chignell said when he arrived at the house he consulted with sergeants and the suspect’s mother as he assessed the situation.”I decided to attempt to make contact with him to get him to surrender,” he said.Chignell said Johns appeared at an upstairs window and, after initially refusing to emerge from the home, he surrendered.”He was agitated, he was profane, he was bloodied, but he was coherent,”Chignell said of Johns.Johns, a convicted felon with a violent history, was arrested without incident and booked into jail on felony counts of making criminal threats, being a felon in possession of a firearm and being a felon in possession of ammunition, Chignell said.Chignell said officers combed the home and located the shotgun and ammunition. Johns’ grandmother was found uninjured.