Life and death situations can happen in 0.5 of a second. Police officers are trained to handle situations in 0.5 of a second.
If police officers handled everything 2 seconds late they would be dead.
The guy put his arm down, and around 2 seconds later they shot him, please actually read my posts since you're clearly not.
Just gonna make it clear for you - The man put his elbow down, if the police there were trained to react in 0.5 seconds, they they would've realised his elbow was down, they had 2 whole seconds to think before they decided "forget it, open fire."