"The airstrike that killed Abu Wahib a few weeks ago, that’s what triggered it, okay?" Mateen told police in one conversation.
Wahib was killed in a May 2016 airstrike by the US-led coalition on Daesh targets in Iraq.
"They [United States] should have not bombed and killed… Wahid," Mateen said.
According to partial transcripts released earlier, Mateen had repeatedly pledged allegiance to Daesh.
Mateen was killed in a final shootout with police on June 12 after killing 49 patrons and staff in the Pulse nightclub in Orlando and wounding 53.