I did a little research on some of the news articles. I was not able to get the Bee archives to find the story that implied the perp. was trained for the way the officer was killed. I will continue to hunt and post if I find it.
Here is part of the Aug 23 account by the local ABC channel. URL Link at the end of the article for the full story by ABC 30.
Telen's fellow officers raced to save his life after he was gunned down inside a foothill home while checking for a burglar.
Sheriff Richard Pierce called the deputy's death an assassination.
Deputy Telen leaves behind two daughters and his wife, who is expecting their third child. The man police say shot Telen is in jail facing murder and burglary charges. Bail is set at more than $6 million for Ramadan Abdullah. Investigators are checking reports that Abdullah had been staying at a Muslim retreat in Badger, not far from the Dunlap shooting. The Muslim center is located on the former Synanon compound. About 50 families moved into the "Muslims of America" camp a few years ago, after converting the 1,800 acre property into a commune.