Baker is the leader of a terrorist cell.
Baker laid low for several weeks while formulating his plans for the Zodiac. During this time, a woman going by the name "Audrey" joined the ranks of his cell.
Upon finalizing his plans to release the Zodiac in the Willis Tower in Chicago, killing all within, Baker led a team to execute the mission.
Posing as a cleaning crew, Baker and his men made their way to the tower's Skydeck shortly before dawn, where they prepared to release the Zodiac as the building filled with people for the day.
Audrey, in truth, was actually Black Widow, who had infiltrated Baker's cell and determined his plans.
With defeat inevitable, Baker sought to escape with the Zodiac by jumping from the Skydeck, and landing safely by way of a personal parachute.
However, Captain America was unwilling to let Baker escape with the Zodiac. He jumped off the Skydeck without a parachute and struggled with Baker in mid-air. Unwilling to die in the fall, Baker released the Zodiac to Cap and activated his 'chute. Captain America was snared in mid-air by Rumlow back on the Skydeck with a grappler arrow.
After he escaped, Baker's current whereabouts are unknown.