Kate is shot, a gun battle ensues with Widmore's men, Claire is left behind with Locke

The moment after Jack pushes Locke into the water, Widmore's men who are hiding at the tree-line take their first shot which hits Kate in the shoulder. Jack, Sayid and Claire open fire on the numerous armed men hiding in trees and behind tall grass.

After Jack empties his gun, he grabs Kate and heads for the submarine hatch. Sayid helps lower her into the submarine as Claire keeps shooting at Widmore's guys. Locke emerges from the water, climbs onto the pier and angrily opens fire on Widmore's men.

After Sawyer finds out what happened, he goes to the top of the hatch and screams for Claire. Locke is at the other end of the pier and screams "James!" and starts running towards the submarine. Sawyer closes the hatch, leaving Locke and Claire on the pier.

Sawyer radios Frank and tells him to get the captain to dive. The captain flips the levers and the submarine starts moving.

Claire sees the sub leaving and screams as she runs towards it. Locke grabs her with a smirk on his face and says "You don't want to be on that sub."

So why did Widmore's men wait until Locke was pushed into the water to open fire? Also, why was Kate, a non-candidate, the only one shot? Widmore mentioned her earlier and knows she's not a candidate. It all seems to a bit too convenient. Is it possible that Widmore has been working on Locke's team this entire time and his appearance otherwise was all a con?