Apache/php High Usage Resolution

Our server has lately been found to be completely unresponsive, and not responding to any of the services including ping and SSH. We want to determine if the high usage comes from high Apache traffic or PHP scripts. Checking the stats from WHM -> Daily process log and found that one user in particular is using a lot of system resources : We need someone that can update / optimize the scripts running under this domain in order to reduce the load this accounts puts on the server. There may even be obsolete scripts that can be removed. The sites is hosted on a Linux Operating System.