Attorney General William Barr suggested in his letter to Congress on Sunday that the public may not know of some actions by President Trump that raised concerns in special counsel Robert Mueller’s obstruction of justice investigation.

In his four-page letter, which stressed the 22-month investigation did not find evidence of collusion between the Trump campaign and Russia, Barr said Mueller left the obstruction question unresolved. A line taken from Mueller’s final says, “while this report does not conclude that the President committed a crime, it also does not exonerate him.”