Why is my robot shooting my friends?

His "Buck Up" skill, which restores shields, shares the same visual effects as his default ranged attack which looks like a blue thunderbolt. When being targeted, the recipient may have a visual cue around their screen border. I have had a coop partner's Deathtrap target me with "Buck Up" even when I was in "FFYL" mode, although I can not confirm whether this had any effect upon gaining "Second Wind".

As a side note, the skill seems to restore more than 30% shields as Deathtrap appears to channel the ability. Maybe it just triggers the shield recharge and it continues to fill the remainder by itself. I feel like the skill warrants more inspection as it allows the Mechromancer to be a big team player in coop!