What should occur when the Imam sits for the final Tashahhud during Salat al-Khawf?

Primary text

When the Imam sits for the final Tashahhud, the first group sits with him, recites the first Tashahhud, and then stands while the Imam is sitting to complete their prayer. They should recite Al-Fatiha and a Surah in every unit because what they are making up constitutes the beginning of their prayer, and they did not obtain the recitation of a Surah with the Imam. The Imam should prolong the final Tashahhud and supplication until they complete their two units, after which he will perform the Tashahhud and conclude the prayer with them.