One of two hostages who died after a 16-hour siege at a Sydney cafe in December was killed by ricocheting fragments of police bullets, an inquest into the deadly stand-off heard. Barrister and mother-of-three Katrina Dawson, 38, died along with café manager Tori Johnson, 34, and Iranian-born gunman Man Haron Monis, 50, when police stormed the cafe in Sydney on December 16. "Ms Dawson was struck by six fragments of a police bullet or bullets which ricocheted from hard surfaces into her body," counsel assisting the coroner's inquest, Jeremy Gormly, said yesterday. "I will not detail the damage done to Ms Dawson other than to say that one fragment struck a major blood vessel. She lost consciousness quickly and died shortly afterwards." The NSW Coroners' Court inquest will outline what happened in the siege, which involved 17 hostages, investigate the response and delve into the background and motivation of Monis. A separate investigation commissioned by the federal and NSW governments is set to submit a report in the next few days. The coroner's inquest will review the report's findings. The stand-off shocked Australians, with thousands laying bouquets at a large makeshift memorial near the Lindt chocolate cafe. Gormly said Johnson was shot in the back of the head by Monis with a sawn-off shotgun after several hostages escaped. "Johnson was made by Mr Monis to kneel on the floor of the cafe. After a short lapse of time, Mr Monis simply shot him without further notice or warning in the back of the head," he said. "The end of the barrel was about 75 cm from Mr Johnson's head at the moment of discharge. Mr Johnson is believed to have died immediately." Gormly said the shooting was witnessed by a police marksman, which led to the order for police "tactical operatives" to force their way into the cafe. Some 22 shots were fired by the officers after 11 flash bangs were thrown into the cafe, while Monis fired two shots, the hearing was told. "Bullets and fragments hit Mr Monis, who was, it seems, killed instantly," Gormly said. "At least two bullets, police bullets or bullet fragments, hit Mr Monis in the head and 11 other bullets, police bullets or fragments, hit him in the body." During the stand-off, Monis fired a total of five rounds from his shotgun, which he took into the cafe early on December 15. None of the rounds struck anyone apart from Johnson, "although he appears to have been trying to do so", Gormly added. The inquest will look into Monis's claims his actions were an attack on Australia by the Islamic State group and whether he had any terrorist associations.