The county he died in might have his estate record. You can either go to the county courthouse or mail them a request for his estate record. Most Pennsylvania counties did record some deaths up to the 1920's and 30's but it will have limited information. The office to contact would be the Register of Wills. Once you have a death date you can try to get his obituary and death certificate.
You might also try the Westmoreland County Historical Society, Derry Area Historical Society and there are a number of local libraries and historical societies throughout Westmoreland County that might be able to help you.
Access to all of Pennsylvania's state death certificates is very restricted and there is no index at all. We are in the process of trying to change that. Go to our website to learn how you can help: http://users.rcn.com/timarg/PaHR-Access.htmhttp://users.rcn.com/timarg/PaHR-Access.htm