In 1898, Angel has his soul returned as part of a curse:
You don't remember. Everything you've done. For a hundred years. In a moment, you will. The face of everyone you have killed — our daughter's face — they will haunt you and you will know what true suffering is
Having his soul returned encourages Angel to be a 'good guy', e.g.
1996: The reclusive and emotionally tortured Angel was sought out by a demon named Whistler, who persuaded him to join the fight against the evil that had corrupted him and to help the newly-activated Slayer, Buffy Summers. Angel traveled to Hemery High School in Los Angeles, where he witnessed Buffy being called as the Slayer and her initial training under her Watcher, Merrick, as well as her emotional suffering over her new duties and her parents' deteriorating marriage. Filled with a new purpose in life, Angel resolved to help the Slayer, with whom he had fallen in love, and moved to Sunnydale, California, where Buffy was predestined to move the following year
However, in S3 E10, the First Evil taunts Angel with the faces of past victims, including a businessman, Travis, who was killed in 1998.
My question is, how is Angel able to kill innocents despite having a soul?
N.B. Angel also killed Travis' children, so the defence of 'maybe Travis was evil' doesn't work here.