Tracy Morgan’s condition is improving, but the “30 Rock” and “Saturday Night Live” star remained in critical condition early Monday morning following a Saturday crash that killed fellow comic James “Jimmy Mack” McNair.

“He has been more responsive, which is an incredibly encouraging sign,” Morgan’s publicist, Lewis Kay, said Sunday.

Prosecutors brought charges against the truck driver, 35-year-old Kevin Roper, who allegedly rear-ended the limo bus that Morgan, McNair, and three other injured parties were riding in. The truck driver worked for Wal-Mart. The company said it “will take full responsibility” if it’s determined that their vehicle caused the accident.

Sgt. Gregory Williams of the New Jersey State Police said the tractor-trailer driver “failed to observe slow-moving traffic ahead. At the last minute, he swerved to try and avoid the Mercedes limo bus but struck it from behind, forcing the limo to rotate and overturn.”

Morgan, 45, had surgery Sunday to repair a broken leg and is expected to be in a New Jersey hospital for several weeks, CBS reported. The comedian also sustained a broken nose and several broken ribs in the crash.

The crash killed 62-year-old McNair, of Peekskill, New York. Roper was freed after posting $50,000 bail over the weekend.