Law enforcement officials on edge after the killings of two Texas prosecutors and Colorado’s prison director got more reasons to worry as a West Virginia sheriff was fatally shot, and Texas authorities arrested a local man for threatening another county official, the Washington Post reports.It is uncertain whether the killings are connected or merely coincidental events in dangerous professions. Mingo County, W.Va., Sheriff Eugene Crum was gunned down yesterday in the spot where he usually parked and ate lunch. In Kaufman County, Tx., judges are being escorted by armed guards to and from work, sheriff's cars are parked outside the new district attorney's house, and secretaries in the county courthouse have been given bulletproof vests. The death rates for law enforcement officers nationally have fluctuated over time, with the most dangerous period in the 1970s. Overall, deaths of officers in the line of duty spiked from 122 in 2009 to 165 in 2011 and dropped to 129 last year, says the Washington, D.C.-based National Law Enforcement Officers Memorial Fund. Over the past three years, however, premeditated attacks on law enforcement officials have spiked, says Glenn McGovern of the Santa Clara County, Ca. District Attorney’s office, who has written two books on the subject.