Around midnight 17 July 1918, Yakov Yurovsky, the commandant of The House of Special Purpose, ordered the Romanovs' physician, Dr. Eugene Botkin, to awaken the sleeping family and ask them to put on their clothes, under the pretext that the family would be moved to a safe location due to impending chaos in Yekaterinburg. The Romanovs were then ordered into a 6 m × 5 m (20 ft × 16 ft) semi-basement room. Nicholas asked if Yurovsky could bring two chairs, on which Tsarevich Alexei and Alexandra sat. Yurovsky's assistant Grigory Nikulin remarked to him that the "heir wanted to die in a chair. Very well then, let him have one." The prisoners were told to wait in the cellar room while the truck that would transport them was being brought to the House. A few minutes later, an execution squad of secret police was brought in and Yurovsky read aloud the order given to him by the Ural Executive Committee:
Nikolai Alexandrovich, in view of the fact that your relatives are continuing their attack on Soviet Russia, the Ural Executive Committee has decided to execute you.Nicholas, facing his family, turned and said "What? What?" Yurovsky quickly repeated the order and the weapons were raised.
You can find other accounts online RE how long it took to actually kill everyone, since the women had crown jewels sewn into their clothes, which impeded bullets.
When the bodies were on their way to be burnt, a Revolutionary peasant-guard stuck his fingers inside the mutilated vagina of Alexandra and then bragged about how he'd fingered the "royal cunt."