Two children enjoying an evening at their local pool were shot on Wednesday when a gunman opened fire at a recreation center in West Philadelphia.

There were around 75 children in the pool at the Christy Rec Center pool at around 4pm, when the unidentified assailant opened fire at people standing on the street outside.

Four people were injured in the attack, including a 10 and an 11 year old, Police Commissioner Kevin Bethel said at an evening news conference.

The two children suffered graze wounds and 'will be fine,' along with an employee at the recreation center.

A fourth individual between the ages of 17 and 20, however, is in 'very critical condition' after being shot multiple times in the back.