The Washington Post first reported details, external about the second strike, which has led to concern from both Democrat and Republican lawmakers.
In response to a reporter’s question during a cabinet meeting on Tuesday, Hegseth said that he watched the first strike “live” but quickly moved on to another meeting.
“I did not personally see survivors,” Hegseth said of the first strike. “That thing was on fire and it exploded… you can’t see anything. This is called the fog of war.”
He added that he learned of Admiral Bradley’s “correct decision” to sink the boat “a couple of hours later”.
“We have his back,” Hegseth said of Bradley.
President Trump, for his part, also defended Adm Bradley, although he distanced himself from his decision to strike the vessel a second time, saying that “we didn’t know about” the follow-on strike.
“And I can say this: I want those boats taken out,” Trump added.
More than 80 people have been killed in a wave of similar strikes across the Caribbean and Eastern Pacific since early September.
The Trump administration has repeatedly defended the strikes as a necessary self-defence measure to save American lives from illicit drugs.