The British government should have done more to rescue hostage Alan Henning, the captive's brother-in-law said according to the BBC.
ISIS militants purportedly beheaded Henning in yet another gruesome online video released Friday.
The British taxi driver was on a volunteer mission delivering aid in a convoy in Syria last December when the Islamist extremists kidnapped him near the Turkish boarder.
Colin Livesey, the brother of the victim's wife, condemned Henning's killers and said the government should have stepped in to rescue him "when they knew about it, months and months ago," the BCC reported.
"My heart's just sunk to a level I never thought it could do," Livesey added. "I'm just devastated for my sister and two kids for what they've gone through, and it's so hard."
Majid Freeman, a friend of Henning who was with him when he was kidnapped, expressed the same feeling the government could have prevented the tragedy.
"They usually give these hostages one week since they make the video, and then they kill them," Freeman told BBC Radio 4, referring to previous videos where the next hostage to be killed is shown at the ending. Henning was shown at the ending of a September video showing the murder of another British hostage, David Haines.
"In Alan's case they dragged it on for three weeks...which goes to show that they did maybe, they were maybe considering releasing him."
Security officials are in the process of authenticating the Friday video, which features a militant who is believed to be a British national from the sound of his accent.
At the video's end, the life of another hostage is threatened, American aid worker Peter Kassig.
British Prime Minister David Cameron called the murder "absolutely abhorrent." A spokesperson for the prime minister said the group's brutality will not stop them from continuing the recently approved air strikes against ISIS targets.
"Indeed, the senseless murder of an innocent man only reinforces our resolve to defeat this terrorist organization and to eradicate the threat they pose to Britons," the spokesperson said according to the BBC.
