Steven Robertson posted a chilling message on social media just hours before he carried out his attacks on his ex-wife and step-daughter.The 40-year-old stabbed Emma Coupland and Nicole Anderson to death before dying in a car crash as he tried to flee the scene.The Record can reveal that police officers are scouring CCTV cameras after witnesses claimed Robertson, who split from Emma last summer, had been seen sitting in his car outside the hospital the night before the fatal stabbings.Posting on