Irvine, CA – The Irvine Police Department (IPD) has identified the suspect involved in a homicide on an Irvine bike path. The suspect is identified as Dennis Thomas Monson, Jr., age 37, transient.
In the early morning hours of Jan. 19, 2016, Monson was with 51-year-old victim Sidney Siemensma, with whom he was acquainted, on a bike path adjacent to the Interstate 405 near Irvine Center Drive behind the Los Olivos residential community. An altercation occurred, and Monson repeatedly stabbed the victim. The suspect then fled the scene.
At approximately 7:00 a.m., IPD received a report of a bleeding man from a jogger, followed by similar reports from passing motorists. IPD responded and located Siemensma, who was determined to be deceased.
Detectives began investigating the case and quickly identified Monson as a possible suspect. That night at approximately 7:20 p.m., an IPD officer patrolling the area located and contacted the suspect on the same bike path where the homicide had earlier occurred.
It was subsequently determined that Monson was in possession of child pornography on his cell phone. The suspect was charged for the child pornography by the Orange County District Attorney (OCDA) and has been in custody on those charges since Jan. 19, 2016.
While Monson remained in custody, IPD continued investigating the homicide, including submitting evidence for forensic testing. Based on the evidence in the case, IPD has identified Monson as the suspect in the murder of Siemensma and the case has been submitted for criminal charges to the OCDA.
It is believed that Monson is the sole suspect in this case and there are no outstanding suspects.
###
IRVINE POLICE DEPARTMENT
One Civic Center Plaza, Irvine, CA 92606
(949) 724-7000 www.irvinepd.org
"Working In Partnership with the Community"
INTEGRITY - QUALITY SERVICE - ACCOUNTABILITY - RESPECT
Since its incorporation in 1971, Irvine has become a nationally recognized city, with a population of 250,384, spans 66 square miles and is recognized as one of America’s safest and most successful master-planned urban communities. Top-rated educational institutions, an enterprising business atmosphere, sound environmental stewardship, and respect for diversity all contribute to Irvine’s enviable quality of life. This family-friendly city features more than 16,000 acres of parks, sports fields and dedicated open space and is the home of the Orange County Great Park – the first great metropolitan park of the 21st century. For more information, please visit cityofirvine.org.