Galvanomagnetic measurements on photocarriers in pure AgCl and AgBr have been extended to an intense electric field (${E}_{x}\ensuremath{\sim}5$ kV/cm) and high magnetic field (${H}_{z}\ensuremath{\sim}58$ kOe) at 4.2 K by using a fast-pulse technique. improved arrangements of blocking electrodes were adopted in order to detect simultaneously the three components of the transient photocurrent, ${Q}_{x}$, ${Q}_{y}$, and ${Q}_{z}$. Substantial roles of the LO-phonon emission in hot-electron kinetics have been revealed and clear pictures of the hot-electron phenomena in silver halides were obtained, for the first time, by a quantitative analysis of the results: (1) At ${H}_{z}=0$, the momentum distribution of electrons (or holes) forms a line connecting the two points $\stackrel{\ensuremath{\rightarrow}}{\mathrm{v}}=0$ and $\stackrel{\ensuremath{\rightarrow}}{\mathrm{v}}=(\ensuremath{-}{V}_{\mathrm{LO}},0,0)$, where $(\frac{1}{2}){m}^{*}{V}_{\mathrm{LO}}^{2}\ensuremath{\equiv}\ensuremath{\hbar}{\ensuremath{\omega}}_{\mathrm{LO}}$, and the electrons are ideally streaming on the trajectory repeatingly emitting LO phonons. Hence, the electron drift velocity at high ${E}_{x}$ at ${H}_{z}=0$ is saturated to $(\frac{1}{2}){V}_{\mathrm{LO}}$. (2) An anomalous distribution of hot electrons involving population inversion predicted by Maeda and Kurosawa, is realized by applying a moderately high ${H}_{z}$ such that $1<\ensuremath{\zeta}<2$, where $\ensuremath{\zeta}\ensuremath{\Xi}{(\frac{2\ensuremath{\hbar}{\ensuremath{\omega}}_{\mathrm{LO}}}{{m}^{*}})}^{\frac{1}{2}}{(\frac{c{E}_{x}}{{H}_{z}})}^{\ensuremath{-}1}$. The distribution consists of two groups of electrons; the first group of electrons are streaming and the second group are accumulated within a high-energy area $K$ in momentum space. Depending on the electron accumulation in the area $K$, the tangent of the Hall angle, $tan\ensuremath{\theta}\ensuremath{\equiv}\frac{{Q}_{y}}{{Q}_{x}}$ and also ${Q}_{z}$ increase abruptly with ${H}_{z}$. (3) It was found that the electron trapping lifetime varies with ${E}_{x}$ and ${H}_{z}$. The streaming motion is responsible for the variation in lifetime. The experimental results here afford, for the first time, a set of conclusive evidence for the streaming motion, the anomalous distribution, and the advent of population inversion of the polarons in momentum space.