Because Trump is very anti 2A.
If you were paying any attention at all, you'd see pretty much every 2A community, advocate and lobbying group was outraged by that statement and made statements against it.
Having said that, it is actually illegal to carry a firearm to go commit crimes like destroying government property, assaulting federal officers and obstructing them in carrying out their constitutional duties.
Of which Pretti did zero of.
We have video of at least three ICE agents executing people in the street with testimony that contradicts what we see with our eyes.
Pursuit is an exception to the warrant requirement, according to a 1976 Supreme Court case: https://www.law.cornell.edu/wex/hot_pursuit