- Sniper (who is meticulous) went through great pains to make a phone call that was untraceable
- The police said 'we can't understand you' which pissed him off
- He didn't call them back with a phone, he immediately shot another victim
I think they tried to get a second call thereby creating the potential for a mistake and the sniper responded with a solid 'up yours'. It's my impression the sniper is in control.