This brigade ( though Shia and therefore with some ties to Iran) has a history of cooperating with the Iraqi govt ( most members are Iraqi) and the Peshmerga Kurds against ISIS, a common enemy. Looks like the US went in and destroyed their weapons.
ISIS must have helped prepare the target list.
Iraqi parliament member Mustafa Sanad:
“Whenever news from the White House claims that US airstrikes are directed against Iranian-backed armed factions that targeted US bases in the region, and that these airstrikes are effective, be sure they are fake news.
All of the strikes are aimed at Iraqi national forces associated with the Popular Mobilization Forces, an official government entity."