Someone is getting fired. Or someone was in on it, uniformed secret service division should have not only marked this position, counter snipers and law enforcement should have been present.
And at that range, a suppressor would be unnecessary.
Generally suppressors on long guns are for the comfort and safety of the shooter, additionallythe drop in muzzle velocity wouldn't be worth it since the shooter didn't care if they knew where the shots were coming from or revealing his hide.
Plus 150 yards is nothing, boots do that with open sights in basic training.