Hackers compromised Dallas emergency system and set off 156 sirens for 90 minutes Friday night. False alarm created panic among Dallas residents who flooded 911 system with 4,400 calls between 11:30 PM and 3 AM. The sirens radio system and repeaters had to be shut down manually on Saturday morning. The Federal Communications Commission and a team of engineers are investigating, but police arent yet involved in the investigation. City officials are convinced the attacker is from the Dallas area.”]