( CNN ) -- A man accused of killing his wife while she frantically spoke to a 911 operator bought marijuana candy just hours before the deadly shooting , police said Thursday . Now Richard Kirk , 47 , faces a first-degree murder charge . And authorities are facing questions about why it took them so long to reach the family 's Denver home . For nearly 13 minutes , Kristine Kirk told 911 she feared for herself and their three scared children . She screamed when her husband went to the family safe and grabbed a gun . The 911 operator heard what sounded like a gunshot . Then `` the screaming stopped , '' Denver Police Detective Mark Crider wrote in a search warrant affidavit . And Kristine Kirk , the detective wrote , was `` never heard from again . '' When they arrived at her house , investigators found her dead on the floor with an apparent gunshot wound to the head . Receipts and security camera footage showed Richard Kirk had purchased a candy called `` Karma Kandy Orange Ginger '' at a marijuana store in southeast Denver at 6:40 p.m. that night , the affidavit says . Investigators said they 'll examine a blood sample to determine whether Kirk was under the influence of any substances at the time of the shooting . During her 911 call made just after 9:30 p.m. , according to the affidavit , Kristine Kirk said her husband `` had taken some marijuana and possibly some prescription medication for back pain . '' `` Please hurry , '' she told the dispatcher , adding that her husband was `` totally hallucinating '' and scaring their kids , the affidavit says . The affidavit says Kristine Kirk sounded `` panicked '' but does not specify at what point in the 911 call her tone changed . After authorities arrested Richard Kirk , the affidavit says , he started `` rambling to himself '' and told an officer `` that he was the strongest in the Church of Latter Day Saints and he had killed his wife . '' At the time , police believed he was under the influence of a controlled substance or prescription medication `` based upon his speech patterns , his inability to focus and his pupils , '' the affidavit says . Colorado became the first state in the nation to legalize the sale of recreational marijuana , allowing pot stores to open for business on January 1 . At a court hearing Wednesday , Richard Kirk was ordered held without bail on an accusation of first-degree murder . In response to questions about the incident , Denver Police Chief Robert White told reporters Thursday he had opened an internal review of why it took officers more than 12 minutes to respond , CNN affiliate KUSA reported . `` We want to know how long it took our officers from the time they were dispatched to get to that particular call , '' he said . Investigators will look at the time it took operators , dispatchers and police officers to handle the call , he said . `` We are going to look at all nuances in this situation . What , if anything , went wrong from our perspective ? What we can do to mitigate instances like that in the future ? '' White said , according to KUSA . A dispatcher has been placed on leave pending the investigation into the incident , the CNN affiliate reported , citing police officials . The city of Denver auditor 's office this year began studying police response times , which have grown longer in recent years , the Denver Post reported . The report is expected in June , and police have cited fewer officers and limited budgets for hiring more officers since 2008 as causes for longer response times , the newspaper reported . Kirk admitted that he killed his wife -- `` without questioning , '' another police document says -- when an officer put him in the backseat of a patrol car , the probable cause document says . Lance Kirk , brother of Richard Kirk , told CNN affiliate KWGN that he was stunned to hear of the incident . `` I know that was n't Richard -- let 's just say that , '' Lance Kirk told the news outlet . `` I hope there are some answers that come out about this . '' Police : Motorist called 911 several times before he died in road-rage shooting . CNN 's Michael Martinez , Mariano Castillo , Stefan Simons , Kara Devlin and Dottie Evans contributed to this report .
Police affidavit : Richard Kirk bought marijuana candy hours before his wife was killed . Denver Police Chief Robert White says he 's conducting an internal review into the response . For nearly 13 hours , Richard Kirk spoke to a 911 operator -- until a gunshot rang out . After the gunshot , an affidavit reads , ` ` was stopped , '' but she was ` ` never heard from again ''